Ocean Current Speed Calculator

The Coriolis Parameter f = 2Ω·sin(latitude) genuinely goes to zero at the equator, and because Geostrophic Velocity is Pressure Gradient divided by (Water Density × Coriolis Parameter), a very small Coriolis Parameter in the denominator produces a very large or unstable velocity. This isn't a numeric glitch -- geostrophic balance, the physics this calculator models, is known to break down near the equator, where real currents follow different equatorial dynamics the formula doesn't capture. Treat any result from a Latitude within a few degrees of 0° as unreliable rather than a literal speed. At exactly Latitude = 0° the Coriolis Parameter is precisely zero and geostrophic velocity is mathematically undefined (division by zero), so the calculator shows "--" there instead of a numeric value.

It depends on Latitude, and Latitude is not the secondary factor here -- near the equator it dominates Geostrophic Velocity unboundedly, since the Coriolis Parameter in the denominator collapses toward zero and the result grows without limit (e.g. moving Latitude from 30° to 0.5° with Pressure Gradient held at its default swings the result roughly 50x, from about 0.013 m/s to about 0.77 m/s, and the swing keeps growing the closer Latitude gets to 0°). Away from the equator, Pressure Gradient's full declared range (0.0001 to 0.1 Pa/m) does move Geostrophic Velocity roughly a thousandfold and Water Density's realistic range (1020 to 1035 kg/m³) only nudges the result by a couple of percent -- but Latitude's near-equator effect is unbounded and can exceed both.

No. The Coriolis Parameter depends only on Latitude and Earth's fixed rotation rate (f = 2Ω·sin(latitude)) -- it's a property of the planet's rotation and your position on it, not of the water itself or the pressure field driving the current. Changing Pressure Gradient or Water Density moves Geostrophic Velocity but leaves the Coriolis Parameter output completely unchanged.

Rossby Deformation Radius estimates the horizontal scale at which Earth's rotation starts to dominate over a disturbance's own dynamics -- roughly the size of the ocean eddies and coastal jets that form at a given latitude -- using an approximate 2 m/s baroclinic wave speed rather than a value measured for your location. Ekman Depth estimates how deep wind-driven surface mixing reaches, using a fixed representative eddy viscosity. Both are order-of-magnitude estimates, not site-specific measurements.

Geostrophic balance sets Geostrophic Velocity equal to Pressure Gradient divided by (Water Density × Coriolis Parameter), so for the same pressure push, denser water requires more force to accelerate to the same speed -- the same reason a denser fluid resists acceleration more than a lighter one under an identical applied force. Across this calculator's realistic seawater density range the effect is small, roughly a couple of percent from top to bottom.